Adjustable Venturi Nozzle for Stable Gas-Air Mixing
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Solution Overview
Problem
Existing fuel gas-air mixing devices face limitations in maintaining precise fuel gas to air ratios at low partial loads due to abrupt changes in pressure loss and control tolerances caused by geometry and component sensitivities, leading to inadequate modulation range and pressure signal variability.
Innovation Solution
The air supply path is designed to be turbulence-free with continuous cross-sectional changes via a flow-enhancing throttle mechanism that moves parallel to the air flow, coupled with an elastic element, allowing the air duct and throttle to shift and adjust the cross-sectional area in response to air pressure differences, ensuring a stable negative pressure and precise control of the gas valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Venturi nozzle is used to maintain constant fuel gas/air ratio, then the mixing ratio remains constant within narrow tolerances over a certain range of air mass flow, but below a limit value the flow velocity becomes too low and the mixing ratio can no longer be maintained
Solution Approach 1:
The patent applies the dynamics principle by making the nozzle cross-section adjustable rather than fixed. The nozzle geometry can be continuously adapted to different operating conditions, allowing the system to maintain proper flow velocity and mixing ratio across the entire modulation range from partial to nominal load. This resolves the contradiction by enabling the nozzle to dynamically adjust its characteristics based on the required output level.
Solution Approach 2:
The invention changes the geometric parameters of the Venturi nozzle, specifically the cross-sectional area, to adapt to different operating conditions. By adjusting the nozzle geometry parameter in response to varying load requirements, the system maintains adequate flow velocity even at low partial loads, thereby preserving mixing ratio constancy across the full modulation range.
2Reliability
If the Venturi nozzle geometry is fixed to ensure constant mixing ratio, then the pressure loss behaves as a square between partial and nominal load, but the total system is limited in nominal load by the maximum possible pressure increase of the blower
Solution Approach 1:
The patent makes the nozzle cross-section dynamically adjustable, allowing optimization of pressure loss characteristics at different operating points. By adapting the nozzle geometry to match the required power output, the system can operate efficiently across the full power range from partial to nominal load without being constrained by blower pressure limitations.
Solution Approach 2:
The invention changes the geometric parameters of the Venturi nozzle to optimize pressure loss at different power levels. By adjusting the cross-sectional area parameter, the system achieves better pressure loss characteristics that enable higher nominal load capacity while maintaining precise mixing ratio control.
3Adaptability or versatility
If gravity or spring-loaded shut-off devices are introduced in the flow path to control opening cross-section, then the mixing device can be adjusted to different operating conditions, but control tolerances increase due to unfavorable flow conditions and sensitivity to component tolerances
Solution Approach 1:
The patent replaces gravity-loaded or spring-loaded mechanical shut-off devices with a pneumatic or electronic control system. This substitution eliminates the control tolerances associated with mechanical components and their sensitivity to manufacturing variations, while maintaining the ability to adapt to different operating conditions through precise control signals.
Solution Approach 2:
The invention uses pneumatic actuation to control the nozzle opening cross-section, replacing mechanical spring-loaded or gravity-based devices. This pneumatic control system provides superior precision and reduced sensitivity to component tolerances, thereby improving control precision while maintaining adaptability to varying operating conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design ensures a wide range of reliable operation with precise fuel gas to air mixing ratios at low partial loads, maintaining a consistent mixing ratio across varying operating conditions and preventing flutter, thus enhancing the modulation range and control precision.
Implementation Method 1
Mixing devices of the generic type are based on a mixing nozzle, usually a Venturi nozzle, in which air is conveyed through the nozzle by means of a fan. In the area of the narrow cross-section of the Venturi nozzle, fuel gas is supplied orthogonally.
Implementation Method 2
The direction of the shift takes place parallel to the air flow direction, so that this shift can be brought about simply by air pressure differences in front of and behind the mixing device. The mixing device is designed in such a way that the flowing air and thus the active air pressure of the composite displaces the air duct and / or the throttle means against an elastic element in the air flow direction.
Data Source
Figure 1~2
AI summary
The mixing device has a mixture nozzle (1) having an air duct (2) through which air is passed. A throttle portion (3) and the air duct are formed aerodynamically and cleanly such that continuous cross-sectional contraction portion (4) is formed in a cross-section between the air duct and the throttle portion. The throttle portion and the air duct are displaced relative to each other in air flow direction such that the cross section area in the region of contraction portion is extended continuously with the increasing reversible air flow rate, if combustible gas supply (5) is opened.